An indwelling catheter is a catheter that is inserted into the bladder and allowed to remain in the bladder for a few hours to several weeks. A Foley catheter is a common type of indwelling urinary catheter. A Foley catheter generally includes a thin, flexible tube that can be inserted into the bladder to drain urine. It is held in place with a balloon at the end that lies inside the bladder (e.g., referred to herein as the inner or proximal end) which is filled with sterile water or gas to prevent the catheter from being removed from the bladder. The urine drains through the catheter tube into a bag and thereafter expelled. The tube of a Foley catheter has two separated channels, or lumens, running down its length. One lumen is open at both ends and allows urine to drain into a collection bag. The other lumen has a valve on an outside end and connects to the balloon at a tip to allow for inflation of the balloon with sterile water or gas.
A common issue with Foley catheters is introduction of infection into the bladder. Risk of infection in the bladder increases significantly the longer the catheter remains in place. In fact, a recent study has found that more than 30 million Foley catheters are inserted annually in the United States and result in over 1 million nosocomial catheter acquired urinary tract infections (CAUTI's) per year. CAUTI's are the second most common cause of nosocomial bloodstream infections and approximately 3% of all patients with a catheter will develop bacteremia. Approximately 80% of urinary tract infections (UTI's) are associated with indwelling Foley catheters. For an acute care hospitalization, CAUTI's can add $500 to $1,000 in direct costs with an additional $3,800 if bacteremia occurs.
Foley catheter based UTI's are attributable to bacteria growth on the surface of the inserted Foley catheter that advances along the shaft of the catheter into the bladder and eventually into the blood stream. Under this model, bacterial growth is directly associated with presence of the catheter and as bacteria moves up the shaft of the catheter, the patient is likely to develop urethritis (infection of the urethra) and cystitis (infection of the bladder). In addition, Foley catheters can cause unnecessary pressure on urethral mucosa which often results in trauma and ischemic necrosis. For example, a Foley catheter can induce inflammation in the urethra coupled with mucosal injury due to presence of a foreign body. The resultant injury to the mucosa coupled with the presence of the foreign body and absence of normal clearance of dead mucosal cells provides a milieu for bacterial overgrowth. The inflammation can also travel up the prostate and result in prostatitis or into the bladder and cause cystitis.
The degree of mucosal injury associated with an inserted Foley catheter is often directly proportional to the size of the catheter. Generally, the larger the diameter of the Foley catheter tube, the greater the pressure on the urethral mucosa and thus the greater amount of resulting trauma and ischemic necrosis. Accordingly, Foley catheter design has aimed to reduce the diameter of the catheter to a minimal diameter that still provides free flow of urine. However, prior efforts at using extremely small diameter catheters have failed for several reasons. For example, a Foley catheter with a smaller outer lumen naturally requires a smaller inner lumen. However, catheters with small inner lumen tends to become obstructed frequently. In addition, Foley catheters with smaller inner and outer lumens do not have axial and longitudinal rigidity. As a result, insertion becomes very difficult, especially in older patients who might have significant bladder outlet obstruction or prostatic enlargement. Further, a Foley catheter tube with a small diameter can result in urinary leakage around the catheter when inserted. This is especially pertinent to older women with weakness of the bladder sphincter but can also be seen in both genders and all ages.
The above-described deficiencies of conventional indwelling catheters are merely intended to provide an overview of some of problems of current technology, and are not intended to be exhaustive. Other problems with the state of the art, and corresponding benefits of some of the various non-limiting embodiments described herein, may become further apparent upon review of the following detailed description.